From the course: Advanced SQL: Logical Query Processing, Part 1
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Dual source query processing - SQL Tutorial
From the course: Advanced SQL: Logical Query Processing, Part 1
Dual source query processing
- [Instructor] Every join no matter type, color, gender or race always begins with a Cartesian product. In a Cartesian product, each row from one set is paired with each row from the other. The result set consists of all columns from both sources. If the specified join type is a cross join, processing stops at this point and the Cartesian product is passed on to the next clause. For all other join types, processing continues to the next step qualification. Inner and outer join are called qualified joins. The qualification predicate is specified using the on keyword. The qualification process evaluates each row from the Cartesian product using the predicate. Only rows for which the predicate evaluates to true will live to see another clause. All other rows are eliminated from the set. If the requested join type is an inner join, join processing stops at this point and only the qualified rows are passed on to the next…
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